Optical imaging devices and methods

ABSTRACT

The present invention relates to optical imaging devices and methods for reading optical codes. The image device comprises a sensor, a lens, a plurality of illumination devices, and a plurality of reflective surfaces. The sensor is configured to sense with a predetermined number of lines of pixels, where the predetermined lines of pixels are arranged in a predetermined position. The lens has an imaging path along an optical axis. The plurality of illumination devices are configured to transmit an illumination pattern along the optical axis, and the plurality of reflective surfaces are configured to fold the optical axis.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation, under 35 U.S.C. § 120, of U.S.application Ser. No. 16/005,008, filed Jun. 11, 2018, which is acontinuation, under 35 U.S.C. § 120, of U.S. application Ser. No.15/246,682, filed Aug. 25, 2016. Each of the preceding application ishereby incorporated herein by reference in its entirety for allpurposes.

STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

Marking of objects with codes for identification is commonly used inboth industrial and commercial environments. For example,one-dimensional (barcode) and two-dimensional codes have been placed onobjects to allow for quick identification of the object based on thedata contained in the codes. Generally, laser based scanning devices andsystems are used to read the codes due to their ability to successfullyscan the code on an object when the object is moved by the scannerquickly. This can allow for laser based scanning devices to have a highscan rate (lines/second), when compared to other scanning devices.

Additionally, laser based systems can be easily commissioned, as areading area of a laser scanner can be clearly marked by the laser line.This can allow users to quickly determine proper alignments of the laserscanner and peripheral devices. Further, laser scanning devices can havelarge viewing angles, (e.g. 60-90 degrees). The large viewing angleallows for laser scanners to be mounted very close to the object to bescanned, or the scanning area (i.e. a conveyor belt) while stillmaintaining sufficient reading area to be able to read a code.

However, laser based devices are subject to multiple regulations, andare generally regulated to limit the amount of energy that the laser canoutput. This regulation of the laser output power can limit thedistances and fields of view (“FOV”) over which the laser based scanningdevices and systems can be used. Additionally, many laser based scanningdevices utilize rotating or vibrating mirrors to generate a moving spot.These moving parts can subject laser based scanning systems toadditional wear and tear, and thereby decrease both reliability andlifespan of the device.

Previously, vision or camera based systems have been used in an attemptto provide an alternate to using laser scanning devices. However,previous vision or camera based systems did not have sufficient scanrates to be able to scan many codes, particularly in applications wherethe codes are required to be scanned quickly. For example, in anapplication where the object is moving at approximately 1 m/s, a laserscanner can scan the code at 1000 lines per second. Thus, the code wouldmove only 1 mm between scans. However, a typical vision or camera basedsystem may have a scanning rate of only 30 frames per second, allowingfor approximately 33 mm of movement between frames. This can result inmissed codes or partially imaged codes, or possibly no capture at all ofthe code in any of the frames.

Further, in camera or vision based scanning systems, the opening angleof the field of view is determined by the focal length of the imaginglens and the sensor size. Generally, these systems have an opening angleof about 30 degrees to about 40 degrees. These opening angles aregenerally smaller than for laser based scanning systems. Therefore, fora camera or vision based scanning system to cover the same field of viewas a laser based scanning system, the camera or vision based scanningsystem must be placed farther from the object to be imaged than a laserbased scanning system. Thus, a solution for increasing a scanning rateof a vision system is needed.

SUMMARY OF THE INVENTION

An optical imaging device for reading optical codes is disclosed. Theimage device comprises an area sensor, a lens, a plurality ofillumination devices, and a plurality of reflective surfaces. The sensoris configured to sense with a predetermined number of lines of pixels,where the predetermined lines of pixels are arranged in a predeterminedposition. The lens has an imaging path along an optical axis. Theplurality of illumination devices are configured to transmit anillumination pattern by producing an illumination path along the opticalaxis, and the plurality of reflective surfaces are configured to foldthe optical axis.

In some embodiments, only the predetermined lines of pixels are used toimage an object. The sensor may have 960 lines of 1280 pixels, and thepredetermined used number of lines of pixels may be 40.

In some embodiments, the plurality of illumination devices are lightemitting diodes. These illumination devices may be configured on a planethat also contains the optical axis. The plurality of reflectivesurfaces can be mirrors. Some embodiments comprise reflective surfacesthat are configured to fold an illumination axis along the same axis asthe optical axis. In some embodiments, folding the optical axis reducesa minimum focused distance to a closest reading plane. Additionally,folding the optical axis may reduce a required mounting space betweenthe device and a closest reading plane. Optionally, an illuminationpattern produced by the illumination devices is conjugated with thesensor predetermined used number of lines of pixels.

The optical imaging device may further comprise an exit window, whereinthe illumination path and the imaging path would exit the opticalimaging device through the exit window. The exit window may additionallyinclude a filter in at least one of the imaging path and illuminationpath to filter a determined band of the light wavelength spectra. Insome embodiments, the exit window comprises multiple filters and thefilters in the imaging path and in the illumination path are polarizedwith crossed directions of polarization.

A method for reading optical codes using an optical device is alsodisclosed. The method comprises focusing an imaging path along anoptical axis using a lens, generating an illumination pattern, foldingthe imaging path using a plurality of reflective surfaces, and sensingan object in the imaging path using an area sensor. The lens isintegrated into the optical device, and the illumination pattern has anillumination path along an axis approximately the same as an axis of theimaging path. The sensor uses only a predetermined number of lines ofpixels available to the sensor.

The method may optionally further comprise folding the illuminationpattern using the plurality of reflective surfaces. The method may alsofurther comprise reducing reflections from the optical codes using afilter, which may be an ultraviolet filter. The optical device mayfurther include an optical filter in at least one of the imaging pathand the illumination path for filtering out a determined band of thelight wavelength spectra. The illumination pattern may be generatedusing a plurality of illumination devices, and the plurality ofillumination devices may be integrated into the optical device.

A folding attachment device for an existing optical imaging device isalso disclosed. The folding attachment device comprises a folded opticalpath portion and a line-shaped illumination pattern generator. Thefolded optical path portion is configured to fold an optical path of theoptical imaging device, and the line-shaped illumination patterngenerator correlates to a windowed portion of a sensor of the opticalimaging device. The line-shaped illumination pattern generator mayoptionally include at least one of a beam splitter and a dichroicmirror. The device may further comprise a tilted exit window to reducereflections into the accessory device, and may be tilted atapproximately 15 to 30 degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a general optical reader field of view determination.

FIG. 2 illustrates an optical reader field of view determination havingan alternate lens focal length.

FIG. 3A is a system view of a general optical reader.

FIG. 3B is a system view of a general optical reader having a singlefold.

FIG. 4 is a graphical representation of a windowed sensor.

FIG. 5 is a graphical representation of a windowed sensor sensing a onedimensional bar code moving in a defined direction.

FIG. 6A is a system view of an embodiment of an illumination devicepattern layout for an illumination path on the same plane as the opticalaxis.

FIG. 6B is an alternative system view of an embodiment of anillumination device pattern layout for an illumination on the same planeas the optical axis.

FIG. 7 is a system view of an alternate one fold optical reader withlonger inner path.

FIG. 8 is a system view of an exemplary imaging system with a multiplefolded optical path.

FIG. 9 is a system view of an embodiment of a multiple reflectivesurface imaging system illustrating the folding of an optical path inthe imaging system.

FIG. 10 is an isometric view of the multiple reflective surface imagingsystem of FIG. 8.

FIG. 11 is a side view of the multiple reflective surface imaging systemof FIG. 8.

FIG. 12 is a cross sectional view of an alternate multiple reflectivesurface imaging system.

FIG. 13 is an alternate embodiment of a multiple reflective surfaceimaging system wherein the illumination is not folded with the imagingpath.

FIG. 14 is an alternative embodiment of a multiple reflective surfaceimaging system having a beam splitter to combine the illumination pathand the optical path.

FIG. 15 illustrates a possible illumination pattern using an opticalimaging device as illustrated above.

FIGS. 16A-16C illustrate multiple embodiments of illumination optics.

FIG. 17 is an alternative embodiment of a multiple reflective surfaceimaging system having a tilted exit window.

FIG. 18 is a process chart illustrating a process for sensing an objectusing an optical imaging system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having” and variations thereof herein ismeant to encompass the items listed thereafter and equivalents thereofas well as additional items. Unless specified or limited otherwise, theterms “mounted,” “connected,” “supported,” and “coupled” and variationsthereof are used broadly and encompass both direct and indirectmountings, connections, supports, and couplings. Further, “connected”and “coupled” are not restricted to physical or mechanical connectionsor couplings.

Additionally, the use of the term “code” can be understood to meanvarious readable codes such as one dimensional “bar codes,”two-dimensional codes (e.g. QD codes, etc.), and other various codetypes. The use of the term code is not limiting to the type of codeapplied.

The following discussion is presented to enable a person skilled in theart to make and use embodiments of the invention. Various modificationsto the illustrated embodiments will be readily apparent to those skilledin the art, and the generic principles herein can be applied to otherembodiments and applications without departing from embodiments of theinvention. Thus, embodiments of the invention are not intended to belimited to embodiments shown, but are to be accorded the widest scopeconsistent with the principles and features disclosed herein. Thefollowing detailed description is to be read with reference to thefigures, in which like elements in different figures have like referencenumerals. The figures, which are not necessarily to scale, depictselected embodiments and are not intended to limit the scope ofembodiments of the invention. Skilled artisans will recognize theexamples provided herein have many useful alternatives and fall withinthe scope of embodiments of the invention.

The use of imaging devices and systems to read codes, or even to performbasic imaging tasks, requires that the imaging device, or reader have aminimum distance from the object to be imaged to ensure proper field ofview and focus can be achieved. In some applications, the availabledistance between a reader and the object to be imaged can, at times, bevery limited. In some examples, the focal length of a lens used in anoptical reader can be modified to reduce a minimum closest focused planedistance. However, reduction of the minimum closest focused planedistance by reducing a focal length can increase the field of viewangle, causing a farthest imaging plane to increase in size. Thisincrease in the size of a farthest imaging plane can reduce theresolution in the farthest imaging plane, thereby making it moredifficult to analyze smaller objects. An example of adjusting a focallength to reduce the minimum focal distance can be seen in thediscussion of FIGS. 1 and 2, below.

FIG. 1 illustrates a general optical reader 100 having a field of view(“FOV”) 102. The reader 100 can be configured to read data between afirst plane 104 and a second plane 106. The first plane 104 and thesecond plane 106 can be separated by a first distance 108. In oneexample, the distance can be 304 mm. However, the first distance 108 canbe more than 304 mm or less than 304 mm. Additionally the first plane104 and the second plane 106 can have defined widths. In one example,the first plane 104 can have a width of 100 mm, and the second plane 106can have a width of 254 mm. The FOV 102 of the reader 100 can thereforebe defined once the size of the sensor and the focal length of a lenswithin the reader are determined. In the example of FIG. 1, assuming aone-third inch sensor, and a 9.6 mm focal length lens, the FOV 102 canbe ±14 degrees, where the first plane 104 and the second plane 106 arearranged as discussed above. This results in a distance 109 between thefirst plane 104 and the reader 100 being approximately 203 mm. Thedistance 109 being 203 mm can be inappropriate for some applications,particularly where space is limited. The FOV 102 can generally bedetermined by the equation

${{\tan\;\alpha} = \frac{s}{f^{\prime}}},$where α is equal to the FOV angle 102, f′ is equal to the focal lengthof a lens, and s is equal to and imaging sensor size. Alternatively, theFOV can be determine by the equation of

${{\tan\;\alpha} = \frac{y}{d}},$where y is equal to half the length of the second plane 106, (shown asdistance 110), and d is equal to the distance from the reader 100 to thefarthest plane 106 (shown as distance 112).

To reduce the minimum focal distance to the first plane 104, the focallength of the lens of the reader 100 can be decreased. Turning now toFIG. 2, an example imaging system 200 can be seen with a reader 202having a lens with a focal length of 4.2 mm. The system 200 can furtherhave a first plane 204 and a second plane 206 separated by a distance208. For purposes of comparison, in this example the first plane 204 andthe second plane 206 are separated by approximately 304 mm. By reducingthe focal length of the lens to 4.2 mm, from the 9.6 mm focal lengthused in the system in FIG. 1, the minimum distance 210 to the firstplane 204 can be reduced to 88 mm, assuming the same one-third inchsensor is used. Further, this changes the angle of a FOV 212 of theimaging path to approximately 30 degrees. Furthermore, the width of thesecond plane 206, assuming the first plane 204 has a width of 100 mm,increases to 455 mm.

While the above examples provide a possible solution for reducing aminimum distance to the object to be imaged by the imaging system byreducing the focal length of the lens, in some examples it may not bepossible to reduce the minimum distance to the object to be imagedenough for a given application. One solution to further reduce the spacerequired between an imaging device and an object to be imaged is to foldthe optical path. In one example, mirrors can be used to fold theoptical path. However, other reflective surfaces can be used to fold theoptical path, such as prisms where internal reflection is produced.

Turning now to FIGS. 3A and 3B, an optical imaging system 300 can beseen. The optical imaging system 300 can have an imaging device 302. Theimaging device 302 can include a sensor 303, one or more illuminationdevices 304 and an imaging lens 306. The optical imaging system canfurther include a reflective surface 308, which can be contained in anenclosure 310, as shown in FIG. 3B. In one embodiment the sensor 303 canbe a CMOS-type sensor. Alternatively, the sensor 303 can be a CCD typesensor, or other type of applicable sensor. In one embodiment, thesensor 303 can be an AR0134 sensor from Aptina. Imaging sensors cangenerally limit the scan speed of an object due to the limited framerate available in many digital imaging sensors. To increase the framerate of a digital imaging sensor, the effective sensing area of thesensor 303 can be reduced. For example, as shown in FIG. 4, a graphicalrepresentation of a sensing area 400 of a sensor can be seen. Thesensing area 400 can contain multiple pixels. The number of pixels in agiven sensing area 400 determines the resolution of a given sensor. Insome embodiments, sensors can have millions of pixels (megapixels). Forexample, common sensor sizes can be 4 megapixels, 8 megapixels, 12megapixels, etc. The higher the number of pixels in the sensing area400, the greater the resolution of the sensor. While greater pixelcounts increase the resolution of a sensor, the increase in resolutioncan have an adverse effect on scanning speed due to the requiredprocessing power associated with the increased number of pixels.

To increase a scanning speed of a sensor without reducing the desiredresolution, the sensing area 400 can be reduced such that only a portionof the sensing face 400 remains active. FIG. 4 shows a first inactivearea 402 and a second inactive area 404 surrounding an active pixel area406. In one embodiment, the active pixel area 406 can be sized to theexpected FOV required to view a particular code. For example, where aone dimensional bar code is expected to be scanned in a particularorientation (i.e. vertical or horizontal), the active pixel area 406 canbe oriented similarly (vertically or horizontally). Further, as only aportion of the width of the given code is required for a one dimensionalcode, the active area 406 can be reduced to a few lines of pixels. Forexample, the active sensing area 406 can be reduced to between 10 linesand 50 lines. However, more or fewer lines of pixels can also be used,as necessary for a given application. In one example, for a sensorhaving a resolution of 960 lines 1280 pixels, and a frame rate of 54frames per second, by using only 40 lines of 1280 pixels, the activesensing area 406 can be reduced by a factor of 24 and the frame rate canbe increased by a corresponding factor of 24. This increase in framerate can allow for increased scanning speed and throughput when using anoptical imaging system. Additionally, the active sensing area 406 can bereduced to a number of lines between 10 and 100. While the activesensing area 406 could be reduced to less than 10 lines, maintaining atleast 10 lines can reduce the effect of dead pixels in the sensor.Further, maintaining at least 10 lines in the active sensing area 406can improve accuracy of an imaging device by providing increasedinformation in comparison to a line sensor.

Turning now to FIG. 5, the sensing face 400 of FIG. 4 is shown imaging aone dimensional bar code 500 as it passes through the sensing face 400in the direction shown. The orientation of the imaged code is such thatthe active sensing area 406 is able to image all of the data in the barcode 500, even though only a portion of the sensing face 400 is active.In one embodiment, the active sensing area 406 can be orientedhorizontally (to coincide with the largest dimension of the sensor) toallow for a larger FOV and a better resolution, and can also be alignedwith the movement direction of the code.

Returning now to FIGS. 3A and 3B, the optical reader 300 can include oneor more illumination devices 304. In one embodiment, the illuminationdevices 304 can be light emitting diodes (“LED”). In some examples, theilluminations devices 304 can be a single color LED. Alternatively,multiple colored LEDs can be used to allow for different wavelengths tobe presented to the object depending on the type of code to be imaged.In some embodiments, the illumination devices 304 can output light at aconstant output. Alternatively, the optical reader 300 can vary theoutput of the illumination devices 304. For example, in someapplications, the code to be read may be on a highly reflective object,where high intensity light can obscure or “wash-out” the code. Thus, theoutput of the illumination devices 304 can be reduced to ensure properillumination of the object. Additionally, the illumination devices maycomprise illumination optics, which are discussed in more detail withreference to FIGS. 16A-16C.

Furthermore, filters located in an exit window 314 of the imaging device300 can be used to filter out ambient light, as shown in FIGS. 3A and3B. Additionally, filters may be designed to filter out a determinedband of the light wavelength spectra, and can filter the imaging path,illumination path, or both. In one example, the illumination devices 304can output light in the ultraviolet spectrum. Further, in some examples,the codes on the objects can be printed using a fluorescent ink, whereinthe emission wavelength is different from the excitation wavelength, theuse of a filter on the imaging path can allow only the fluorescenceemission wavelength provided by the fluorescent ink to pass through;thereby allowing only the object of interest (the code) to be imaged.

Additionally, cross-polarized light can be used to avoid reflections onthe objects to be imaged. This feature is advantageous where the code tobe imaged is on a shiny or reflective surface, such as a polished metalobject. To polarize the light, a polarizer can be placed in front of theillumination devices 304, and a polarizer with the polarizing directionperpendicular to the illumination polarizer can be placed in the imagingpath. In one embodiment, the polarizer can be integrated into the exitwindow 314. Alternatively, the polarizer can be incorporated into theillumination devices 304 and into the imaging lens. Further, thepolarizer can be placed directly in front of the illumination devices304 and in front of the imaging lens. In some embodiments thepolarization direction of the imaging path can be parallel to theillumination polarizer; alternatively, the polarization direction can beperpendicular to the illumination polarizer. Generally, the orientationof the polarizer is selected based on the application.

The one or more illumination devices 304 can further be oriented suchthat the light is transmitted along approximately the same axis as anoptical imaging axis 312. In some embodiments, the illumination devices304 are configured on a plane that contains the optical imaging axis312. In one embodiment, the illumination devices 304 can transmit lightalong a similar but separate axis from that of the optical imaging axis312. However, as both the optical imaging axis 312 and the illuminationaxis are approximately the same due to the use of the reflective surface308, both axis can be close enough such that the illumination devices304 provide illumination in the field of view of the optical reader 300.

In one embodiment, one or more illumination devices 304 can be used.Further, to help match an illumination pattern geometry to an imagingpath or to coincide with a sensing area, such as active sensing area 406discussed above. One example of positioning the illumination devices canbe seen in FIG. 6A. FIG. 6A illustrates a plurality of illuminationdevices 600 and an imaging lens 602 positioned in an illumination optic604. As shown in FIG. 6A the illumination devices 600 can be arrangedlinearly. Further, the illumination devices 600 can be equallydistributed on either side of the imaging lens 602. Alternatively, theillumination devices 600 can be distributed unevenly, or in a non-linearpattern, as applicable. The illumination device 600, as arranged in FIG.6A, can project an illumination pattern similar to the active sensingarea 406 of FIGS. 4 and 5.

The illumination optic 604 can be produced in a number of ways. In someembodiments, the illumination devices 600 are placed within an injectionmolded part, e.g., the illumination optic 604, and can take on anydesired shape, such as those shown in FIGS. 16A-16C for non-limitingexamples of the illumination optics. In some embodiments, an aperturecan be included for the imaging path. In some embodiments, theillumination optics are formed in a single injection molded part, likethat shown in FIG. 6A. In other embodiments, illumination optics may begrouped together, such that a plurality, but not all of the illuminationoptics are positioned in a group of injection molded parts, as shown inFIG. 6B. In yet other embodiments, the illumination optics arepositioned individually. It has been further contemplated that otherpolymer forming processes can be used, such as thermoforming,compression molding, blow molding, and others known in the art.

In some embodiments it is desirable to have the illumination devices 304provide illumination along the same axis as the optical imaging axis.For example, when the imaging device is in close proximity to the objectto be imaged, it can be advantageous to provide illumination in linewith the optical imaging axis. For example, it can be advantageous toprovide illumination along the same axis as an optical imaging axis whenimaging objects over long distances, as where there is an angle betweenthe imaging path and the illumination path, the illumination, after acertain distance, can be partially or totally outside the FOV. By havingthe illumination path in line with the optical imaging axis, theillumination will generally illuminate the FOV. This can further allowfor increased efficiency when imaging objects over longer distances.

Additionally, by providing the illumination in line with the opticalimaging axis, commissioning and set up of the optical imaging system 300can be aided by allowing a user to use the illumination as a guide tounderstand exactly where the imaging path is. Thus, by providingillumination in line with the optical axis, an advantage of a laserbased scanning system can be incorporated into an optical imagingsystem. In some embodiments, a beam splitter (for example, a 50%transmission, 50% reflection beam splitter) can be used to converge theillumination axis with the optical imaging axis. However, other opticalmanipulation devices can also be used. For example, a dichroic filtercan be used in lieu of a beam splitter when different wavelengths areused for the illumination and imaging paths, such as when fluorescentimaging is used.

The reflective surface 308 of the optical reader 300 can be used to“fold” the imaging path, as shown in FIG. 3B. In one embodiment, thereflective surface can be a mirror. Alternatively, other reflectivematerials, such as prisms, can be used. The reflective surface 308 canallow for the optical reader 300 to be placed near the closest desiredreading plane. For example, the imaging lens 306 of the optical reader300 can have a 4.2 mm focal length, such that to maintain the desiredFOV described above would make the minimum focused distance 88 mm. Thiswould generally require a closest reading plane to be at least 88 mmaway from the imaging lens 306. In some applications, the distance tothe first focused plane needs to be smaller, for example, 30 mm.However, by positioning the reflective surface 308 at a 45 degree angle,the optical imaging axis 312 can be folded at a 90 degree angle. Thiscan allow the optical reader 300 to be positioned closer to the closestreading plane. In the present example, assuming that the reflectivesurface 308 is positioned approximately 30 mm from the focal lens 306and 30 mm from the exit window 314 of the enclosure 310, 60 mm of the 88mm minimum focus distance can be located within the optical imagingsystem 300, thereby requiring only a distance of 28 mm between the exitwindow 314 of the optical imaging system 300 and the closest readingplane.

Turning now to FIG. 7, an alternative embodiment of the optical imagingsystem 300 of FIG. 3 can be seen. FIG. 7 illustrates an optical imagingsystem 700, the optical imaging system 700 can include an imaging device702. The imaging device 702 can include a sensor 702, one or moreillumination devices 704, and an imaging lens 706. In similarembodiments, the one or more illumination devices 704 can be located inthe same horizontal plane as the imaging lens 706. In embodiments suchas this, a plurality of illumination devices 704 may be located oneither side of the imaging lens 706, such as in the orientation ofillumination devices 600 and imaging lens 602 shown in FIG. 6A, 6B, orthose other orientations discussed above. The optical imaging system canfurther include a reflective surface 708 which can be contained in anenclosure 710. However, in this embodiment, the reflective surface 708can be positioned approximately 65 mm from the focal lens 706 and 25 mmfrom an exit window 712 of the enclosure 710. This can allow for zerodistance between the exit window 712 of the optical reader 700 and aclosest reading plane, where the imaging lens 706 has a 4.2 mm focallength. Thus, FIG. 7 illustrates a possible modification to the imagingpath within the optical imaging system 700 to allow for the minimalfocused distance to be contained completely within the optical imagingsystem 700. This can allow for additional flexibility when integratingthe optical imaging system 700 into an application.

Turning now to FIG. 8, a further embodiment of an optical imaging systemcan be seen. FIG. 8 illustrates an optical imaging system 800. Theoptical imaging system 800 can include an imaging device 802. Theimaging device 802 can include a sensor 803, one or more illuminationdevices 804, and an imaging lens 806. The optical imaging system 800 canfurther include a first reflective surface 808, a second reflectivesurface 810 and a third reflective surface 812. The reflective surfaces808, 810, 812 can be contained within an enclosure 814. In thisembodiment, the imaging and illumination paths can be folded by thereflective surfaces 808, 810, 812 to allow for an alternative enclosure814 design. Similar to above, the reflective surfaces 808, 810, 812 canbe positioned to allow for the entire minimum focused plane distance tobe contained within the enclosure 814, such that no additional distanceis required between the exit window 816 and the closest reading plane.However, the reflective surfaces 808, 810, 812 could also be positionedto minimize the enclosure 814 size, while also limiting the additionaldistance required between the exit window 816 and the closest readingplane, as applicable. While the optical imaging system 800 is shown withthree reflective surfaces, more than three reflective surfaces or lessthan three reflective surfaces can be used, as applicable.

In some examples, the multiple reflective surface optical reader 800 canbe used in applications where the focal length of the imaging lens 806requires a greater minimum focal length. For example, FIG. 9 shows adetailed view of a multiple reflective surface optical imaging system900. The optical imaging system 900 can include an imaging device 902,the imaging device 902 including a sensor 903, one or more illuminationdevices 904, and an imaging lens 906. The imaging system 900 can furtherinclude an optical folding device 907, the optical folding device 907can include a first reflective surface 908, a second reflective surface910 and a third reflective surface 912. In one embodiment, the imagingdevice can be a DM150 or DM260 from Cognex. Further, a communicationconnection 914 can be seen coupled to the imaging device 902. In oneembodiment, the communication connection 914 can provide communicationbetween the imaging device 902 and a processing device (not shown) suchas a PC, or dedicated image processing system. In one embodiment, thecommunication connection 914 can communicate via a serial connection,such as RS-262, RS-485, Universal Serial Bus (“USB”), or via otherprotocols such as Firewire, Ethernet, ModBus, DeviceNet, or otherapplicable communication protocol. In a further embodiment, thecommunication link 914 can be a wireless communication link. Forexample, the communication link 914 can provide communication with otherdevices, such as the processing device discussed above, using wirelessprotocols such as Wi-Fi, Zigbee, Bluetooth, RF, cellular (3G, 4G, LTE,CDMA), or other known or future developed wired or wirelesscommunication protocols. Additionally, the communication connection 914can be used to provide power to the imaging device 902. Alternatively,the imaging device 902 may have an alternate power source, such asbattery power, or a separate external power supply connection.

In this example, the imaging lens 906 can have a focal length of 6.2 mm.Thus, assuming that the first imaged plane is approximately four incheswide, the minimum object distance would be 131 mm. However, using theequations described above, a minimum focal length can be determined forany given closer and/or farther plane widths. Further, where the imaginglens 906 lens has a 6.2 mm focal length, the optical reader 900 can bedesigned to allow for 68 mm of the minimal focused distance to be foldedbetween the reflective surfaces 908, 910, 912. To do so, the distance(d1) between the focal lens 906 and the first reflective surface 908 canbe 15 mm; the distance (d2) between the first reflective surface 908 andthe second reflective surface 910 can be 25 mm; and, the distance (d3)between the second reflective surface 910 and the third reflectivesurface 912 can be 28 mm. Thus, a remaining distance of 63 mm isrequired between the third reflective surface 910 and an object plane916 to achieve the minimal focused distance.

As the imaging and illumination planes are “folded” between thereflective surfaces 908, 910, 912, the FOV of the imaging planeincreases, requiring the reflective surfaces 908, 910, 912 to increasein size after each “fold.” Using the values discussed above, reflectivesurface 908 would require a dimension of about 40 mm about the longaxis. Reflective surface 910 would require a dimension of about 60 mmabout the long axis, and reflective surface 912 would require adimension of about 85 mm about the long axis. The size of the individualreflective surfaces can be determined using the equation

${{\tan\;\alpha} = \frac{L\text{/}2}{d}},$where α is the FOV angle, L is the length of the mirror, and d is thedistance between the mirror and the reader (or, alternatively, betweenmirrors in a multiple mirror system). Thus, by varying the distances andsizes of multiple reflective surfaces, the imaging path can be “folded”to allow for a more compact installation by reducing the physicaldistance required between an imaging device and a first imaged plane.

Additionally, while the above optical imaging system 900 described as anentire system, in some embodiments it may be desirable to modify anexisting imaging device (e.g. imaging device 902) by incorporating anoptical folding device (e.g. optical folding device 907) onto theexisting imaging device, to allow for existing devices to be modifiedaccordingly.

Turning now to FIG. 10, an isometric view of the optical imaging system900 described above can be seen. Here, the FOV of the optical imagingpath 1000 can be seen. As seen in FIG. 10, the FOV can have asubstantially rectangular shape, to coincide with the imaged surface1002. The shape can be chosen for processing optical codes 1004 that maybe passing through the imaged surface 1002 in the direction shown. Therectangular shape can be caused by the windowed sensor, as discussedabove. FIG. 10 further illustrates an enclosure 918 surrounding theimaging device 902, and the reflective surfaces 908, 910, 912. FIG. 11shows a side view of the optical imaging system 900. As seen in FIG. 11,an angle of the FOV of the optical imaging path 1100 can be seen as theimage path exits the enclosure 918. In the example discussed above, theoutput angle can be about 21 degrees.

Turning now to FIG. 12, an alternative embodiment of a multiplereflective imaging system 1200 can be seen. The imaging system 1200 caninclude an imaging device 1202. The imaging device 1202 can be animaging device as discussed above. The imaging device 1202 can beattached to a folding device 1204 via an adaptor plate 1206. The foldingdevice 1204 can include a first reflective surface 1208, a secondreflective surface 1210, a third reflective surface 1212 and an exitwindow 1214. The folding device can further include illumination devices1216. The illumination devices 1216 can be a plurality of LEDs. Further,the folding device 1204 can include an optical lens 1218. The opticallens 1218 can be positioned at the output of the illumination devices1216. In one embodiment, the optical lens 1218 can create a line patternusing the output from the illumination devices. As discussed above, thiscan aid in commissioning and setup of the imaging system 1200 byallowing a user to visualize where the optical imaging path is located,and to improve the illumination system efficiency. For example, theoptical lens 1218 can be used to shape the illumination to match aconjugate active portion of a sensor 1222 in the imaging device 1202 tomatch the illumination pattern to the imaging path FOV.

Turning now to FIG. 13, a further embodiment of an optical reader can beseen as optical reader system 1300. The optical reader system 1300 caninclude an imaging device 1302 having an imaging lens 1304, a firstreflective surface 1306, a second reflective surface 1308, and a thirdreflective surface 1310. The optical reader system 1300 can furtherinclude one or more illumination devices 1312. In the embodiment of FIG.13, the illumination devices 1312 can be located at the exit of theoptical reader system 1300 and adjacent to an exit window 1314. This canallow for an illumination axis 1316 to have generally the same axis asan imaging axis 1318. Further, the illumination devices 1312 can beconfigured to project light such that the imaging object 1320 isilluminated throughout the imaging FOV 1322.

Turning now to FIG. 14, a further embodiment of an optical reader systemcan be seen as optical reader system 1400. The optical reader system1400 can include an optical imaging device 1402 having an imaging lens1404, a first reflective surface 1406, a second reflective surface 1408,and a third reflective surface 1410. In one example, the optical imagingdevice 1402 can be an optical imaging device as described above. Theoptical reader system 1400 can also include one or more illuminationdevices 1412. In one embodiment, the illumination devices 1412 can bepositioned behind the first reflective surface 1406. The reflectivesurface 1406 can be configured to allow the illumination to pass throughthe first reflective surface 1406 and to align an illumination axis 1414with an imaging axis 1416. In one embodiment, the first reflectivesurface 1406 can be a beam splitter. Alternatively, the first reflectivesurface 1406 can be a dichroic filter. By aligning the illumination axis1414 with the imaging axis 1416, an imaging object 1418 can beilluminated on axis through the imaging FOV 1420.

FIG. 15 illustrates an illumination distribution pattern 1508 where anillumination path is transmitted along the same, or similar, axis as anoptical imaging path. Here, the imaging FOV 1502 is shown as beingprojected from an optical imaging system 1504. Similarly, theillumination distribution pattern 1508 within the imaging FOV 1502 isshown projected onto an imaging object 1506. As seen in FIG. 15, themost intense illumination is shown in the darker portions of theillumination distribution pattern 1508, which is elongated in shape tocoincide with the imaging FOV 1502. This distribution of illuminationshown in illumination distribution pattern 1508 can provide fullillumination of the imaging object 1506 to allow for more efficient andaccurate imaging. If the sensor in the optical imaging system 1504 iswindowed to a predetermined number of lines of pixels, as describedabove with reference to FIGS. 4 and 5, the illumination field 1500 canbe conjugated with that number of lines of pixels, such that theillumination field 1500 does not extend beyond the imaging FOV 1502.Although the imaging FOV 1502 is constrained in FIG. 15, it is importantto note that the illumination field 1500 can extend beyond the imagingFOV in multiple directions.

Turning now to FIGS. 16A-16C, a plurality of illumination optics 1600,1602, and 1604 can be seen. FIG. 16A illustrates an exemplary image of afreeform illumination lens 1600. The freeform illumination lens can bespecifically formed to shape and/or pattern illumination from anillumination device. FIG. 16B illustrates an exemplary image of acylindrical lens 1602 for use with an illumination device. Finally, FIG.16C illustrates a reflective optic 1604 for use with an illuminationdevice, in this example a total internal reflection (TIR) lens. Each ofthe illumination optics 1600, 1602, 1604 described above can be used tohelp shape and or pattern illumination from an illumination device, suchas those described above.

Turning now to FIG. 17, a further embodiment of an optical reader systemcan be seen as optical reader system 1700. The optical reader system1700 can include an optical imaging device 1702 having an imaging lens1704, a first reflective surface 1706, a second reflective surface 1708,and a third reflective surface 1710. The optical imaging device 1702 canalso include one or more illumination devices 1712. The illuminationdevices 1712 can be configured to align an illumination axis with animaging axis. The optical reader system 1700 can further include an exitwindow 1714. In one embodiment, the exit window 1714 can be tilted at anangle to reduce reflections along the imaging axis. In one embodiment,the exit window 1714 can be angled. In some embodiments, the exit window1714 is angled at approximately 15 degrees. However, the exit window canbe angled at more than 15 degrees or less than 15 degrees, asapplicable. For instance, the exit window may be angled at approximately30 degrees. Further, while the exit window 1714 is shown in FIG. 17 asangling from left to right, the direction of the angle can be modifiedfor use in a given application to provide the optimal amount ofreflection reduction.

Turning now to FIG. 18, a process 1800 for sensing an optical code usingan optical imaging system as discussed above, can be seen. At processblock 1804 an illumination pattern can be generated. In one embodiment,the illumination pattern can be generated using a plurality ofillumination devices as discussed above. Further, in some embodimentsthe illumination pattern can be shaped or filtered as described above,at process block 1805. For example, the illumination pattern may beshaped using beam splitters, dichroic filters, and/or by positioning theillumination devices in a pattern corresponding to a desiredillumination pattern, and placed within the illumination path. In oneembodiment, the illumination devices can be LEDs. At process block 1802the imaging path can be focused using a lens of an optical imagingsystem. In one embodiment, the imaging path can be focused based on thefocal length of the lens.

At process block 1806 the imaging path can be folded. In someembodiments, the imaging path can be folded using a plurality ofreflective surfaces. For example, mirrors can be used to fold theimaging path, as described above. Folding the imaging path can allow forsome or all of the minimum focus distance to be contained within theoptical imaging system. Reduction of the focus distance by folding theimaging path is discussed in more detail above. At process block 1808,the imaging path can be filtered. In some optional embodiments, theimaging path is filtered at an exit window of the optical imagingsystem. For example, the exit window may have an ultraviolet filter, apolarized filter, a dichroic filter, or other filter as applicable. Theexit window can also be tilted to provide filtering to reducereflections from being returned along the imaging path. The exit windowcan be tilted between 0 and 30 degrees, such as, for example 15 degrees.In some embodiments, the sensor can be windowed 1812 such that only apredetermined portion of the sensor is used to sense objects. Asdiscussed above with reference to FIGS. 4 and 5, windowing can increasethe sensing speed and refresh rate of the sensor by reducing the activepixel area. Finally, at process block 1810, an object in the imagingpath can be sensed via the sensor of the optical imaging system.Additionally, in some embodiments, the image is registered and processedafter the completion of process block 1810.

While the above embodiments describe imaging systems having one or threereflective surfaces arranged as in the figures, these embodiments arenot meant to be limiting. It is understood that using the above methodsand systems, imaging systems can be designed to be accommodated intovarious applications and systems.

What is claimed is:
 1. An optical imaging device for reading opticalcodes; the device comprising: an area sensor; a lens, the lens having anoptical axis forming a portion of an imaging axis of the optical imagingdevice; a plurality of illumination devices, the illumination devicesconfigured to transmit an illumination pattern; an exit window angled atleast 15 degrees to the imaging axis; and a reflective surface disposedalong the imaging axis between the lens and the exit window, thereflective surface configured to fold the imaging axis.
 2. The device ofclaim 1, wherein the illumination devices are configured on a plane thatcontains the optical axis.
 3. The device of claim 1, wherein a distancealong the imaging path between the reflective surface and the exitwindow is at least 25 millimeters.
 4. The device of claim 1, wherein thereflective surface is configured to fold an illumination axis along thesame axis as the imaging axis.
 5. The device of claim 1, wherein thearea sensor comprises a first plurality of lines of pixels, the areasensor configured to sense with only a second plurality of lines ofpixels, the second plurality of lines of pixels arranged in apredetermined position of the area sensor and including fewer lines ofpixels than the number of lines of pixels in the first plurality oflines of pixels.
 6. The device of claim 1, wherein an illumination pathproduced by the illumination devices and the imaging path exit theoptical imaging device through the window.
 7. The device of claim 6,wherein the exit window includes a filter in at least one of the imagingpath and illumination path to filter a determined band of the lightwavelength spectra.
 8. The device of claim 7, wherein the exit windowcomprises multiple filters and the filters in the imaging path and inthe illumination path are polarized with crossed directions ofpolarization.
 9. The device of claim 1, wherein the sensor has 960 linesof 1280 pixels, and the predetermined used number of lines of pixels is40.
 10. The device of claim 1, wherein folding the imaging axis reducesa required mounting space between the device and a closest reading planeby incorporating at least two-thirds of an imaging path between the lensand the closest reading plane within the optical imaging device.
 11. Amethod for reading optical codes using an optical device; the methodcomprising: generating an illumination pattern, the illumination patternhaving an illumination path along an illumination axis approximately thesame as an imaging axis of an imaging path; focusing the imaging pathalong an optical axis using a lens, the lens integrated into the opticaldevice; folding the imaging path using a reflective surface that isconfigured to fold the imaging axis; illuminating an object in theillumination path via an exit window that is angled at least 15 degreesto the imaging axis; and sensing light from an object in the imagingpath using an area sensor, wherein the light from the object is receivedat the area sensor via the exit window, the reflective surface, and thelens.
 12. The method of claim 11, wherein the area sensor comprises afirst plurality of lines of pixels, the area sensor configured to sensewith only a second plurality of lines of pixels, the second plurality oflines of pixels arranged in a predetermined position of the area sensorand including fewer lines of pixels than the number of lines of pixelsin the first plurality of lines of pixels, the second plurality of linesof pixels are aligned in parallel with a direction of movement of theobject being sensed.
 13. The method of claim 11, further comprisingfolding the illumination path using the reflective surface.
 14. Themethod of claim 11, wherein the optical device includes an opticalfilter in at least one of the imaging path and the illumination path.15. The method of claim 11, wherein the illumination pattern isgenerated using a plurality of illumination devices.
 16. A foldingattachment device for an existing optical imaging device; the devicecomprising: a folded optical path portion, the folded optical pathportion comprising a reflective surface configured to fold an imagingpath of the existing optical imaging device; and an exit window angledat least 15 degrees to the imaging path, wherein the reflective surfaceis configured to fold the optical path between a lens of the existingoptical imaging device and the exit window.
 17. The device of claim 16,further comprising a line shaped illumination pattern generator, theline shaped illumination pattern generator correlating to a windowedportion of a sensor of the optical imaging device, wherein the lineshaped illumination pattern generator includes at least one of a beamsplitter and a dichroic mirror.
 18. The device of claim 17, wherein adistance along the folded optical path portion between the reflectivesurface and the exit window is at least 25 millimeters.
 19. The deviceof claim 16, further comprising an adaptor plate configured to mount thefolding attachment to the existing optical imaging device.
 20. Thedevice of claim 19, wherein the tilted exit window is tilted atapproximately 15 to 30 degrees.